Animal exercise wheels are often used in animal cages, such as for mice, rats, other rodents, or other animals.
Wheels, in the prior art, are in two common forms: an open wheel and a curved, rotating dish. Common wheels suffer from three problems: first, it can toss the animal outside the wheel or dish; second, the wheel or dish may accumulate bedding or detritus from the cage; and third, openings may injure the animal.